1. Field of the Invention
This invention relates to solderless electrical connections, and is particularly concerned with insulation-opening electrical connections and a method and apparatus for making a crimped, insulation-opening electrical connection.
2. Description of the Prior Art
The prior art generally recognizes many types of crimped electrical connections. For example, a contact lug may be provided with a sleeve-type connecting portion in which one section is folded tightly about a stripped end of a conductor, while another section is folded tightly about the insulation adjacent the stripped end. Apparatus for accomplishing this crimping operation generally includes a pair of dies and apparatus for moving at least one of the dies toward the other to squeeze the appropriate contact portions therebetween.
It is generally well known in the art to press an insulated conductor, either solid wire or stranded wire, into an insulation-opening notch of a terminating portion of an electrical contact. One such contact is disclosed by Paul Hoppe Jr. in U.S. Pat. No. 3,867,005 as comprising a pair of insulation-piercing notches, each of which is formed by a pair of inwardly extending detents in parallel side walls of a U-shaped portion of an electrical contact. In his U.S. patent application Ser. No. 482,457, issued June 1, 1976 as U.S. Pat. No. 3,959,868, Istvan Mathe discloses a hand tool for inserting an insulated conductor into an insulation-opening contact of the type disclosed in U.S. Pat. No. 3,867,005. Inasmuch as it sometimes is desirable to insert and terminate a plurality of insulated conductors at the same time, the insertion blade is provided in multiple as disclosed by Nijman et al in their U.S. patent application Ser. Pat. No. 432,484, filed Jan. 11, 1974, now U.S. 3,952,392, issued Apr. 27, 1976.
The term "insulation-opening" as used herein is meant to encompass all techniques in which the insulation covering a core of solid or stranded wire is cut, pierced pressed, broken or torn open by one or more elements to gain access and electrical contact to the core.
Although the insulation-opening techniques provide a good electrical and mechanical connection, it has been found that in certain instances, a loosening effect of the connection may occur. This is particularly a problem with stranded conductors which undergo distortion during insertion and which have a clamping pressure applied thereto by the insulation-opening contact elements. The subsequent application of tensile forces, axially and/or transversely, to the conductors held by such pressure causes a relaxation type of deformation and strand movement and repositioning so as to effect a drop in connection pressure. Of course, this condition is highly undesirable and should be eliminated.